The present invention relates to a rear part structure of a vehicle body and more particularly to a vehicle body rear part structure carrying thereon a fuel tank filled with a gaseous fuel such as hydrogen.
Fuel-cell vehicles are known, which comprise an electric motor rotatably driven by electric energy generated from a fuel cell supplied with hydrogen and oxygen (air). In some known fuel-cell vehicles, a fuel tank filled with hydrogen is mounted on a rear part of the vehicle body for supplying hydrogen to the fuel cell.
One example of such vehicle body rear part structure is disclosed in Japanese Patent Laid-open Publication No. 2000-219050, entitled xe2x80x9cCylinder Mounting Structurexe2x80x9d. The disclosed structure includes a small-diameter cylinder and a large-diameter cylinder both disposed below a rear floor panel. The small-diameter cylinder is located below a vehicle rear seat, and the large-diameter cylinder is located below a luggage compartment provided behind the vehicle rear seat. The small- and large-diameter cylinders (or fuel tanks) are carried on a cylinder holder. The cylinder holder has a mid member extending crosswise between left and right side members of the vehicle body and connected at opposite ends to the side members so as to support a central portion of the cylinder holder with respect to the vehicle body.
In the disclosed prior structure, since the mid member is so arranged as to extend in and along a channel-like space defined between lower halves of the small- and large-diameter cylinders or tanks, the opposite end portions of the mid member must be bent upward for enabling attachment of the mid member relative to the vehicle body. The mid member having such bent end portions is, however, susceptible to deformation or yielding when the vehicle is subjected to an impact force. The potential deformation of the mid member is considered when the size of the cylinders is determined. Thus, the relatively easy-to-deform mid member used in the cylinder holder considerably limits the maximum capacity of the cylinders.
It is accordingly an object of the present invention to provide a vehicle body rear part structure which is highly stiff and hence can accommodate fuel tanks of larger capacity in spaces defined in the vehicle body rear part structure.
To achieve the foregoing object, according to the present invention, there is provided a rear part structure of a vehicle body, comprising: a left rear frame and a right rear frame extending longitudinally of the vehicle body; a plurality of parallel spaced cylindrical fuel tanks disposed horizontally between the left and right rear frames, the cylindrical fuel tanks having longitudinal axes extending normal to the left and right rear frames and located below the center of a height of the left and right rear frames; and a cross member disposed between two adjacent ones of the fuel tanks and extending between the left and right rear frames.
Since the axes of the fuel cylinders are located below the center of the height of the left and right rear frames, upper halves of the two adjacent cylinders define therebetween a generally V-shaped space or channel extending normal to the left and right rear frames. The V-shaped channel is used to accommodate the cross member which is straight or of a rectilinear configuration. The cross member preferably has a straight or rectilinear configuration, and the straight cross member is stiffer than the curved or bent cross member used in the conventional vehicle body rear part structure. The rear frames reinforced by the straight cross member is highly resistant to deformation and can accommodate fuel tanks of larger capacity.
In one preferred form of the invention, the left and right rear frames are each formed from a bent frame including a first straight portion extending in a longitudinal direction of the vehicle body, a slanting portion extending obliquely inward from a rear end of the first straight portion toward a longitudinal centerline of the vehicle body, and a second straight portion extending from a rear end of the slanting portion in the longitudinal direction of the vehicle body. The straight cross member extends between the slanting portions of the left and right rear frames.
When the bent rear frames are subjected to a compressive force, they tend to deform at the slanting portions. However, by virtue of the cross member extending between the slanting portions, deformation of the slanting portion does not occur and the fuel tanks are thus reinforced for protection against damage.
The cross member may have opposite end portions flared such that each of the flared end portions extends at an angle of from 90 to 180 degrees relative to the longitudinal axis of the slanting portion of a corresponding one of the left and right rear frames.
The cross member having such flared end portions can bear a larger part of an impact force applied to rear ends of the left and right rear frames without causing stress concentration at the junction between the cross member and the left and right rear frames.